Sodium beta-alumina has a very high two dimensional conductivity and has been know to be a good ionic conductor, but by orienting the alumina layers in the plane of the substrate, the mobile sodium ions are confined creating a dielectric layer.

We have developed sol-gel-beta-alumina films as transistor gate dielectrics that have negligible leakage current and high capacitance. This allows for low voltage transistor operation while remaining transparent. Zinc tin oxide-based semiconductors with indium tin oxide (ITO) gate electrodes gave electron mobilities of 28.0 cm2 V-1 s-1, with an on/off ratio of 2×104. ZTO semiconductors over a lower-temperature, amorphous dielectric, had a mobility of 10 cm2 V-1 s-1. This dielectric was also deposited on flexible polyimide-aluminum foil substrates for organic and solution-processed n-type oxide transistors. This dielectric could have important applications in transistors and in devices employing organic electronics, like e-books.

Related

• Solution-deposited sodium beta-alumina gate dielectrics for low-voltage and transparent field-effect transistors (Nature Materials, Volume 8, 2009, pgs. 898-903)
• New transparent insulating film could enable energy-efficient displays (JHU Press Release)
• Seeing clearly (The Economist, Nov. 12, 2009)